DENVER — Members of the largest employee union at Qwest Communications International Inc. have voted to authorize a strike if talks fail to produce a new contract.

Communications Workers of America District 7 said 93 percent of voting members had authorized union leaders to call a strike if needed.

A contract covering about 20,000 union workers at Qwest expires 12:01 a.m. Aug. 17, a little more than a week before the Democratic National Convention in Denver. The Republican National Convention begins Sept. 1 in St. Paul, Minn.

Denver-based Qwest is providing communication services at both conventions and has committed $6 million worth of cash and in-kind services to each one.

Even if a new contract isn't reached before the existing one expires, union members wouldn't necessarily go on strike, but leaders could choose to call one.

The last time CWA held a strike at Qwest was in 1998, District 7 spokesman Al Kogler said Sunday.

Critical issues include health care, retirement benefits and raises.

The talks cover workers in the 13 states of Colorado, Arizona, Iowa, Idaho, Minnesota, Nebraska, New Mexico, North Dakota, Oregon, South Dakota, Utah, Washington and Wyoming.

Qwest employees in Montana are represented by the International Brotherhood of Electrical Workers.